Epidemiology, Risk Factors and Outcomes of Transition of Acute Kidney Injury to Chronic Kidney Disease in Critically Ill Patients

Acute kidney injury is a life threatening and disabling complication of critical illness encountered in 25 -50%h of intensive care unit admission.Acute kidney injury is a complex clinical syndrome,associated with high short and long- term morbidity and mortality in critical ill patients.

Acute kidney injury outcomes may vary from a complete resolution to a partial or incomplete recovery of renal function leading to increased mortality,prolonged hospitalization and risk of chronic comorbidities like cardiovascular disease,chronic kidney disease and subsequent progression to end stage renal disease.Several studies have suggested a causal link between acute kidney injury and the consequent development of chronic kidney disease.the severity,frequency and duration of acute kidney injury are key factors in this process.

The precise mechanism of transition of acute kidney injury to chronic kidney disease is complex and not completely understood,especially in humans and several pathways have been proposed. Different animal studies have used ischemia-reperfusion and nephrotoxic injuries to investigate the pathophysiologic event involved in acute kidney injury to chronic kidney disease transition ,mainly focusing in the development of specific histological changes .Acute kidney injury outcomes depend, at the tissue level,upon the balance of adaptive and maladaptive repair. An adaptive response to injury usually leads to renal recovery with a complete resolution of pathological changes during acute kidney injury episode(resolution of inflammatory cell infiltration, regeneration of tubular cells,decrease in biomarkers of injury )without long term consequences .However,severe and repeated injury can result in a maladaptive repair,characterized by a permanent reduction in kidney function associated with significant structural changes (persistent expression of pro-fibrotic factors and development of interstitial fibrosis, delayed resolution of inflammation,permanent cell cycle arrest of tubular cells, microvascular rarefaction,renin angiotensin system activation).

The incidence rate of renal progression following acute kidney injury has been estimated to be 4.9 events /100 patient-year and is particularly increase in elderly.